The inner surfaces of tubes, such as steam generator tubes, are usually inspected by means of a mechanical probe having a plurality of spring loaded feelers attached thereto. By monitoring the deflections of the springs through the use of strain gages mounted on the feelers, deposits and/or obstructions within the tube can be determined. However, inasmuch as only a relatively small number of feelers can be utilized due to space limitations and these feelers are in a spaced apart relationship, inspection of the entire inner periphery of the tube cannot be accomplished. In addition, since the feelers contact the inner surface of the tube and are spring loaded, there is always the risk of damaging extremely fragile tubes during such inspection. And lastly, the use of such a mechanical type probe does not permit the user to actually view the deposits and/or obstructions within the tube being inspected.
Because of the foregoing, it has become desirable to develop a non-contact inspection probe which allows the user to visually inspect the entire inner periphery of a tube.